Jean Roy dit Laliiberte, the "dit" usually mean a given name from the army but in this case he suppose to have gotten it because when he got off the boat he cryed out "la liberte" freedom and it stuck to him. That is also why almost non of his children have use the name and it got lost by the second generation.

proy1new has given one explanation of LaLiberte, but perhaps you might also consider this which I venture to suggest is the correct explanation.

Explanation of ‘dit’: Surnames and family names are critically important to genealogical research. The importance of surnames is matched by that of given names and ‘nicknames’. Male ‘nicknames’ usually appear in contemporary documentation as ‘dit’ names – ‘dit’ literally means ‘called’. Acadian ‘dit’ names are often the only means of distinguishing family members with similar given names for example when a man is identified solely by such a given name as ‘Jean’ – a name probably shared by his brothers.

Jean Roy dit LaLiberté, also known as Jean Le Roy was a fisherman from St Malo in France. The nickname by which he was known – ‘dit LaLiberté’ – translated is ‘freedom’. In researching our family story I found references by a Canadian historian Brenda Dunn, Historian Emeritus, Parks Canada, to the fact Jean Le Roy may have been of African descent. His nickname LaLiberté may indicate a slave background though to date I have found no proven evidence to support the theory.